1. Field of the Invention
The subject invention relates to window panes for vehicles and a method of bonding an electrical connector to an electrical conductor applied to the window pane.
2. Description of Related Art
Glass window panes for vehicles, such as windshields, backlites (rear windows), and side windows, frequently include electrical conductors applied to a glass substrate of the window pane. The electrical conductors are typically formed of a silver paste and include one or more pads with a number of leads extending from the pad. The electrical conductors can serve a number of purposes, such as heaters, radio or cellular phone antennas, or keyless entry circuits.
A connector is bonded to the pad to provide electrical communication between a device, such as a heater controller, radio, cell phone, etc., and the electrical conductors. The connector is adapted to receive an end of a wiring harness from the heater controller, radio, cell phone, etc. The connectors can be bonded to the pad by adhesives or can be soldered to the pad through the use of lead soldering techniques. As is known to those skilled in the art, lead soldering requires an external heating of the glass substrate which melts a lead solder and the connector to metallurgically bond the connector to the glass substrate. Traditionally, the connectors also include lead which minimizes mechanical stresses between the connector and the glass substrate during thermal expansion.
Although often effective, the prior art lead soldering is undesirable as lead is considered an environmental contaminant. The lead solder can also crack, which causes the connector to detach from the glass window. Further, the heating involved can cause cracking in the glass substrate.
The prior art has attempted to overcome the deficiencies with lead soldering by developing alternative techniques. One such alternative is disclosed in U.S. Pat. No. 5,735,446. The '446 patent utilizes a friction welding technique that rapidly rotates the connector and simultaneously applies pressure to the connector against the glass substrate. Portions of the connector and the conductor on the glass substrate melt and then re-solidify to create a metallurgical bond between the connector and the conductor. Although avoiding the issues with lead soldering, the friction welding technique of the '446 patent has a number of deficiencies. First, this rotating technique requires that the connector be symmetrical, which greatly reduces the design options for the connectors. Also, the melting of the connector and conductor is an undesirable affect in that the conductor can be completely removed from the glass substrate thereby creating a disconnect between the connector and conductor. Further, the rapid rotation and/or pressure can create undesirable mechanical and thermal shocks that could fracture the glass substrate.
Accordingly, it would be desirable to develop a method of bonding a connector to a conductor that eliminates the use of lead and avoids the deficiencies of the prior art methods.